These days people have increasingly high expectation on life quality. As a result, they also have a higher hygienic demand in daily activities and facilities, notably public toilet facilities. In the past, many public toilet facilities have to be manually operated with hands. Now, many of them are operable automatically by detecting user's use conditions through sensors. Hence in the past users have to shake hands after washing and result in spraying water around, then an improvement was made by providing retrievable paper towels for wiping hands. These days environmental protection awareness increases gradually and protection of trees becomes an increasing focus. Thus the paper towels are gradually displaced by hand dryers.
There are numerous types of hand dryers on the market. They mainly adopt a principle of using a motor to rotate blades to suck in air, heat the air and deliver the heated air. Namely the whole operation includes three elements of “air intake”, “heating” and “air delivery”. To dry the hands within a short time period with reasonable power consumption, every producer tries to alter and adjust the aforesaid three elements. For instance, to save energy consumption in the “heating” element, the heating temperature is lowered but the power for “air delivery” could increase to blow the hands with a greater airflow speed to dispel water from the hands. Some hand dryers attempt to increase the “heating” temperature but reduce the power of “air delivery” to dry the hands. Some other hand dryers focus on design of “air intake” location to recycle the heated air and save energy. However, trying to achieve an effective balance of the three elements of “air intake”, “heating” and “air delivery” remains the core technique of all types of hand dryers. As energy saving is a prevailing trend now, to meet this end design has gradually shifted to delivering high pressure airflow to reduce electric power consumption in the “heating” step. Thus drying hands with high pressure airflow becomes an increasing focus in the design of hand dryers at present.
While designing the hand dryer with a high airflow pressure to save electric power is the prevailing trend at present, it also creates noise problem. The biggest sources of the noise are vibration and airflow shearing caused by the air inlet structure. The conventional air inlet structure adopts a mesh type or shutter type structure to avoid sucking in external articles and prevent incidental intrusion of user's hands.
To reduce the airflow shearing at the air inlet, some hand dryers provide a longer air passage between the air inlet and motor blades to inhibit noise generation. Such an approach greatly increases the size of the hand dryer. The position of the air inlet is restricted and motor air intake efficiency also suffers, that result in even more shortcomings. Hence trying to make structural change to reduce the noise is not a desirable approach. The present hand dryers of high airflow pressure mostly have the air inlet close to the motor blades to increase air intake efficiency. There is no effective way to reduce the noise. The noise problem still exists to date. To provide an air intake structure that can inhibit noise in the condition of a shorter distance between the air inlet and motor is still an issue remained to be resolved.